This invention relates to direction finding systems for generating a direction signal specifying the direction of progress of a vehicle or the like.
As for the prior art system of this sort, Japanese Patent Disclosure No. 123358/1974 discloses a "direction finding system", in which two different electric signals obtained from a magnetic-sensing element are compared in a comparator with two respective reference voltages, and the output signals from the comparator are appropriately combined in a logic circuit to produce eight different patterns to provide a direction signal as the output signal of the logic circuit.
In the system, however, since the two electric signals from the magnetic-sensing element are compared with the respective two reference voltages, if the pair of electric signals from the magnetic-sensing element are abnormally increased due to disturbance of the external magnetic field by external environments, uniformity of 4N heading or bearing divisions specified by the outputs of the logic circuit is lost, and unbalance of the adjacent two bearing divisions, for instance adjacent bearing divisions for specifying the "North" and "North West" directions respectively, occurs in proportion to the extent to which the two electric signals from the magnetic-sensing element are abnormal.